Final answer:
The term 'hard factor' is not recognized in the context of radioactivity or atomic structure discoveries. Instead, Henri Becquerel discovered radioactivity, while Marie Curie named the phenomenon 'radioactivity' and together with Pierre Curie, isolated radioactive elements. Ernest Rutherford further investigated different types of radioactive emissions and contributed to the atomic structure understanding.
Step-by-step explanation:
The notion of 'hard factor' is not mentioned in recognized historical accounts pertaining to the discovery of atomic or nuclear phenomena, which suggests the term might be a misnomer or a typo within the original question. Nonetheless, the discovery of radioactivity, which seems to be the underlying concept here, was a landmark event in scientific history.
Henri Becquerel first discovered the phenomenon of radioactivity, but it was Marie Curie who coined the term 'radioactivity' to describe the spontaneous emission of energy rays by matter. Together with her husband Pierre Curie, Marie Curie significantly advanced research into radioactivity, isolating novel and intensely radioactive elements such as polonium and radium.
Subsequent to these discoveries, Ernest Rutherford, often hailed as the 'father of nuclear physics', expanded on this area of study by investigating and naming the different types of radioactive emissions, leading to considerable advancements in the understanding of atomic structure.